Apparatus for forming master cams



Feb. 27, 1940. A. L. NELSON 2,191,898

AYPARATUS FOR FORMING MASTER CAMS Filed Sept. 28. 1937 ATTORNEY.

Patented Feb. 27, 1940 2,19L

UNI-TED STATES PATENT OFFICE APPARATUS FOR FORMING MASTERL- CAMS Adolph L. Nelson, Detroit, Mich, assignor to Bohn Aluminum & Brass Corporation, Detroit, Mich. a corporation of Michigan Application September 28, 1937, Serial No. 166,196

2 Claims. (Cl. 51-101) This invention relates to method and appagrinding wheel will'be followed consecutively beratus for forming master cams used to grind artiginning .at the point A. h v 'cles to oval or other non-circular form. 1 At the point A the low part of the eccentric An important feature of the invention resides permits the cam blank to move the maximum I in the fact that an eccentric, a simple geometric distance toward the grinding wheel. While the formthat is veryeasy to produce in an accurate cam'blank rotates 90, namely, the sector AB, the shape, is used to guide the forming instrument. eccentric, which is rotating at twice the speed of In certain operations, such as in finishing pisthe cam blank has turned through '180", and has tons for automobile engines, it is sometimes demo ed t e C blank e maximum distance w y sired to give the finished article a slightly oval from the grinding-wheel. While the cam blank w instead of a cylindrical form. This is usually turns through the next 90, namely, the sector done at the time the pistons are being finished on BC, the eccentric completes its first revolution and a grinding wheel, and the accepted method of the low part of the eccentric is again in control at producing the oval shape is to regulate the movepo C, Similarly the Second revolution of e II mentof the grinding wheel relative to the piston e ce t c o tr he 0r -t 0n 0f the Semi 35 by means of an oval master cam. circular cam contour C, D, A.

The prior art method of forming these master Although different mechanical arrangements cams was to calculate certain points on the cam might be u to Carry Out this method, a p eand then to interpolate the rest of the cam. This ferred app atus s us at d in Fi s. 3 and 4- m laying out"involves considerable labor anda cam In this appar u a Cradle Suitably pivoted thus laid out is not absolutely accurate over its at H and for movement about a horizontal entire periphery because of irregularities-which axis Carries a head Stock and a tail Stock mar its form. I A work spindle I5 is journaled in the head stock In carrying out the present invention the master and t e WO k Center s is djustably mounted in oval cam is formed mechanically by using an the tail stock in a well-known manner. A shaft eccentric to reciprocate the cam blank relative is held between the Centers 011 the o Spindle t th ri di h l during t process f grindl5 and the work center l6, and the cam blank i8 ing th master cam In t i process a perfe tly is firmly attached to shaft IT, as by the bolts l9. regular oval contour is generated on the cam The grinding Wheel 20 is set in a fixed position .30 blank mechanically and expeditiously. and is rotated by any suitable source of power. In the drawingz n An eccentric 2| is keyed to the work spindle 55, Fig. 1 is a diagram illustrating the methodl' and by reason of its engagement with a stationary i 2 is a longitudinal section partly in eleva idler wheel 22 causes rocking of the frame I? tion of an apparatus incorporating the invention. with consequent d e of the Cam blank Fig. 3 is a diagrammatic cross-section taken on relative to the fi h Wheel The W0 Tk 35 e 3-3 of Fig. 2. spindle is rotated 1n a suitable manner as by the Fi 4 is a die rammatic cross-section taken on pulley I v the lgine -4 of Fig. 2. The shaft I1 is driven from the work spindle The method of t present invention consists i 5 by suitable reduction gearing which causes essentially in rotating a cam blank in contact Shaft to rotate f g g of t i with a rotating grinding wheel and in moving the In the form of t i 1 us m e a gear 5 cam blank relative to the grinding Wheel by means keyedzsto gt g :g gi i 2'51; i g including an eccentric. Means is provided for gear w m as e Same ear 24. A car 26 kc ed to shaft ll is in turn rotating the cam blank at a predetermined speed griven by splglr gear 21 {which has half the 65 slower than the rotation of the eccentric. Thus, ber of teeth of gear 2 and which is attached to where an oval cam. which may be called a twogear The Spur gear is mounted on th float;-

lobed" is to be produced, the Cam blank is ing arm 28 which is anchored against rotation rotated at f the speedof the eccentricby a link 29 connecting it to the cradle iii. A

e application of this method is illustrated spring 30 biases the cradle l0 toward a position d a rammatically in Fig- 1 Where the dotted line in which the eccentric 2i engages the idler 22,

II) shows the original round contour of the cam and earn blank i8 engages the grinding wheel Zil.

blank and the oval line i I shows the finished oval When this machine is operated the rotation of contour of the master cam. The operation of this the eccentric 2| against idler 22 causes the cam 55 eccentric in reciprocating the blank relative to the blank l8 to reciprocate twice relative to the 55 grinding wheel during a single rotation of the cam blank, which action is illustrated in Fig. '1 and has been described above. Since the eccentric causes the cradle to reciprocate in an 5 even and uniform motion, the oval curve of the finished cam blank will have an even and accurate contour. The amount'of difference between the major and minor axis of the finished cam depends of courseupon the amount of eccentricity given to the eccentric.

The oval cam thus produced may be'called a two-lobed cam. By suitable changes in the gearing so as to cause the cam blank to rotate at different speeds relative to the eccentric, cams having morethan two lobes can be produced. Thus if the cam rotates at or the speed of the eccentric, cams having three or four lobes would result.

I claim:

1. In combination, a pivoted cradle having head stock and a tail stock, a work spindle journaled in the head stock, an eccentric keyed to the work spindle, means for driving the work spindle, a work center adjustably mounted in the tail stock, a shaft mounted between and concentric with the work, spindle and the work center, said shaft being rotatable relative to the work spindle, reduction gearing connected'to the work spindle and to the shaft and causing the shaft to rotate at a slower speed than the work spindle, a cam blank mounted on the shaft and rotatable therewith, a grinding wheel mounted in a fixed position relative to the pivot Qft he' cradle, and an, idler wheel mounted in a fixed position relative to the grinding wheel, and means for I resiliently pressing the eccentric against the idler wheel, thereby causing the grinding wheel tov selectively remove material from the periphery of the cam blank to produce a geometrically uniform cam having a plurality of lobes.

2. In-combination, a pivoted cradle having a head stock and a tail stock, a work spindle 'jo'urw naled in the head stock, an eccentric keyed to the work spindle, means for driving the work spindle, a work center adjustably mountedin" the tail stock, a shaft mounted between and coricentric with the work spindle and the work center, said shaft being rotatablerelative to the work spindle, reduction gearing connected to the a fixed position relative to the pivot of the cradle, and an idler wheel mountedin a fixed. position relative to the grinding wheel, and means for resiliently pressing the eccentric against the idler wheel, thereby causing the grinding wheel to selectively remove material from the periphery I of the cam blank to produce a geometrically uni-- form oval cam.

ADOLPH L. NELSON. 

